An ultra wide band (UWB) receiver with an adaptable analog notch filter is known from an article by Burak Kelleci et al, titled “Narrowband interference suppression in multi-band OFDM ultra wideband communication systems: a mixed mode approach” published in the Digital Signal Processing Workshop, 12th—Signal Processing Education Workshop, 4th Volume , Issue , September 2006 Page(s):55-59. Kelleci describes a receiver made up of the adaptable analog notch filter, followed successively by an AGC circuit (Automatic Gain Control circuit) and ADC (Analog to Digital Converter), FFT processor (Fast Fourier Transform) a digital filter and a demodulator. An adaptable “notch filter” is a filter with a frequency dependent response with a zero or near zero response at an adaptable, isolated frequency. The demodulator demodulates data using phase and amplitude values of frequency components computed by the FFT processor.
Furthermore, an output of the FFT processor is used to determine the frequency of a narrow band interfering signal. This information is used to control the notch frequency of the adaptable analog notch filter, so that the amount of power of the narrow band interfering signal that enters the signal chain is minimized. In addition the frequency of a narrow band interfering signal is signaled to the digital filter, which removes the frequency components at the frequency of the narrow band interfering signal.
Kelleci et al describe the filtering operation as a subtraction of a unity gain narrowband filtered signal from a unity gain wide band filtered signal. The resulting frequency response is symmetric across DC
Kelleci et al describe an iterative tuning process to learn the mapping from the digital information about the frequency of the narrow band interference signal to the setting of the analog notch filter characteristics. An initial calibration factor is applied to the digitally measured frequency in order to select a setting of the notch filter. The calibration factor is iteratively increased or decreased until a maximum suppression of the narrow band interference signal is achieved.
Kelleci et al. also describe that the notch filter may be periodically switched off to determine whether the narrow band interfering signal has disappeared.